Problem: Simplify the following expression: ${7(-z-3)-2(-7+7z)}$
Answer: Distribute the ${7}$ into the first set of parentheses: $ {7(}\gray{-z-3}{)} - 2(-7+7z) $ $ {-7z-21} - 2(-7+7z) $ Distribute the ${-2}$ into the parentheses: $ -7z-21 {-2(}\gray{-7+7z}{)} $ $ -7z-21 + {14-14z} $ Rewrite the expression to group the ${z}$ terms and numeric terms: $ {-7z - 14z} {-21 + 14}$ Combine the ${z}$ terms: $ {-21z} {-21 + 14}$ Combine the numeric terms: $ {-21z} {-7}$ The simplified expression is $-21z-7$